Diaphragm structure of light-sound converter

ABSTRACT

A diaphragm of an optical-acoustic transducer, which improves placement and a shape of a suspension in a cantilever form, and is compact with high performance and suitable for mass production, is provided. In the optical-acoustic transducer in which a light emitter and a light receiver are placed to oppose to a reflecting portion formed on a vibrating section of a diaphragm constructed by connecting the vibrating section and a supporting portion with cantilevers, light is irradiated to the reflecting portion from the light emitter, and a reflected light from the reflecting portion is received with the light receiver to detect a position of the vibrating section, the cantilevers are formed by performing slit working for the diaphragm, portions between an outer circumference edge of the vibrating section and inner circumference edges of the cantilevers and portions between an inner circumference edge of a supporting portion and outer circumference edges of the cantilevers are partitioned by the slit working, and the cantilevers extend along an outer circumference of the vibrating section.

TECHNICAL FIELD

[0001] The present invention relates to an optical-acoustic transducerand more particularly to a diaphragm structure thereof.

BACKGROUND ART

[0002] As a conventional acousto-electric transducer using light(hereinafter referred to as an optical-acoustic transducer), there isknown an optical-acoustic transducer shown in FIG. 13, in which a planediaphragm 11 is fixed to a frame 4 via a ring 3, a light emitter 5 and alight receiver 6 are further fixed to the frame 4, and light irradiatedfrom the light emitter 5 and reflected at the diaphragm 11 is receivedat the light receiver 6, whereby a position of the diaphragm 11 namely,a vibration is converted into an electric signal.

[0003] In an optical acoustic transducer shown in FIG. 13, a diaphragmis flat, and therefore compliance of the diaphragm 11 cannot be madelarge. To eliminate the disadvantage, in a conventional optical-acoustictransducer shown in FIG. 14, the cross section of the part from thecenter of a diaphragm 12 to a perimeter portion is formed in acorrugated form so that a valley and a peak are formed, the perimeterportion is fixed to the frame 4, and the light emitter 5 and the lightreceiver 6 are fixed to the frame 4.

[0004] In a conventional optical-acoustic transducer shown in FIG. 15, adome-shaped reflecting portion 13 a is provided at a center of adiaphragm 13, corrugation is formed from the reflecting portion 13 a toa perimeter portion, a supporting portion 13 b provided at the perimeterportion is fixed to the frame 4, and the light emitter 5 and the lightreceiver 6 are fixed to the frame 4.

[0005] In order to reduce the optical-acoustic transducers in size andtransduce sound with high sensitivity, it is necessary to reduce thediaphragms in size and increase compliance. An optical-acoustictransducer, which is proposed in Japanese Patent Application No.2001-184530 in response to the requirement, is shown in FIG. 16 and FIG.17.

[0006] Namely, an optical-acoustic transducer using a diaphragm 14,which is provided with a dome-shaped reflecting portion 14 a at a centerand a corrugation between the reflecting portion 14 a and a supportingportion 14 b, is further improved by cutting predetermined spots of thediaphragm 14 with laser light or the like to form arc-shaped slits 15 aand spiral slits 15 b.

[0007] The supporting portion 14 b of the diaphragm 14 is fixed to theframe 4. Though the illustration of a light emitter and a light receiveris omitted in FIG. 16 and FIG. 17, the light emitter and the lightreceiver are fixed to the frame as in the above-described prior arts.The spiral slits 15 b and the arc-shaped slits 15 a constructcantilevers 14 c, 14 c, . . . , and a substantially maximum outer sideportion of a vibrating section, whereby amplitude performance of thediaphragm 14 is improved and performance of the optical-acoustictransducer is enhanced.

[0008] However, it is obvious that the optical-acoustic transducers inthese days have extremely increasing requirement for reduction in size,and to respond to the requirement for size reduction, the diameter ofthe vibration plate 14 formed in the dome shape as shown in FIG. 16cannot help being made small. Since part of the vibrating plate 14 iscut in this example, the proportion occupied by the cantilever area isincreased and the area of the diaphragm 14 is reduced as the diameter ofthe diaphragm 14 becomes smaller, and as a result, it cannot be deniedthat the structure of this diaphragm is such that an air pressurereceiving area cannot help being reduced.

[0009] The aforementioned Japanese Patent Application No. 2001-184530describes that it is preferable to provide a rib structure at an outerside portion of the adjacent vibrating section when suspension of thecantilevers 14 c is provided at part of the diaphragm 14, but the shapeof the diaphragm 14 becomes a complicated three-dimensional structure,and as a matter of course, there arises the problem that the productioncost of the forming die and the like of the diaphragm 14 tends to behigh.

DISCLOSURE OF THE INVENTION

[0010] This invention is made to solve the above-described problems, andhas its object to provide an optical-acoustic transducer with theperformance being improved, which makes it possible to reduce cost andis suitable for mass production, by improving and developing thestructure: especially, the shape; and the placement and shape of thesuspension in a cantilever form, of the diaphragm proposed in theaforementioned Japanese Patent Application No. 2001-184530 by theapplicant of the present invention.

[0011] In order to solve the above-described problems, attention is paidnot only to the shape of the suspension in the cantilever form but alsoto the position for placement, in obtaining the shape of the suspensionin the cantilever form. In this case, in order to receive the vibrationof air efficiently, it is obvious that the larger the area of thevibrating section of the diaphragm, the better, as a matter of course.

[0012] However; with the method of providing the suspension in thecantilever form up to the middle of the diaphragm as in the prior art,if the diameter of the entire diaphragm except for the reflectingportion is set to be small, the proportion occupied by the suspension inthe cantilever form naturally has to be larger.

[0013] In order to solve the above problem, as means for vibrating thevibrating section of the diaphragm made by forming a thin film such as afilm, especially, the diaphragm with a small diameter, with compliancebeing reduced, the structure, in which a flat portion with the crosssectional shape extending in the horizontal direction further to theoutside from an outer circumference portion of the vibrating sectionprovided outside the reflecting portion is provided at the entirecircumference, slit working as fine as possible is applied to the flatportion in the state following the outer circumference shape of theaforementioned vibrating section, or the outer circumference portion ofthe vibrating section provided outside the reflecting portion, and thesuspension in the cantilever form is placed, can be considered.

[0014] Consequently, the diaphragm structure of the optical-acoustictransducer of this invention is used for an optical-acoustic transducerin which a light emitter and a light receiver are placed to oppose to areflecting portion formed at a vibrating section of the diaphragm formedby connecting the vibrating section and a supporting portion withcantilevers, light is irradiated to the aforesaid reflecting portionfrom the aforesaid light emitter, and the reflected light from theaforesaid reflecting portion is received with the aforesaid lightreceiver to detect a position of the aforesaid vibrating section, and ischaracterized in that the aforesaid cantilevers are formed by performingslit working for the aforesaid diaphragm, and a portion between an outercircumference edge of the aforesaid vibrating section and innercircumference edges of the aforesaid cantilevers and a portion betweenan inner circumference edge of the aforesaid support portion and outercircumference edges of the aforesaid cantilevers are partitioned by theaforesaid slit working, and the aforesaid cantilevers extend along anouter circumference of the aforesaid vibrating section.

[0015] In the aforesaid diaphragm structure, a slit for partitioning theportion between the outer circumference edge of the aforesaid vibratingsection and the inner circumference edges of the aforesaid cantileversand the portion between the inner circumference edge of the aforesaidsupporting portion and the outer circumference edges of the aforesaidcantilevers comprises: at least three arc-shaped inner slits formed atthe outer circumference of the vibrating section; at least threearc-shaped outer slits existing outside the inner slits and formed atthe inner circumference of the aforesaid supporting portion; and radialslits each coupling one end of each inner slit and one end of the outerslit formed outside the other inner slit adjacent to the one end of theinner slit.

[0016] In the aforesaid diaphragm structure, one end of the aforesaidcantilever is connected to the aforesaid vibrating section by a portionbetween the one end of each of the inner slits at a side to which theradial slit is coupled, and the one end of the other inner slit adjacentto the inner slit, at a side to which the radial slit is not coupled,and the other end of the cantilever is connected to the aforesaidsupporting portion by a portion between the one end of each of the outerslits at a side to which the radial slit is coupled, and one end of theother outer slit adjacent to the outer slit, at a side to which theradial slit is not coupled.

[0017] In the aforementioned diaphragm structure, a flat portionextending further to an outside from an outer circumference edge of theaforesaid reflecting portion is provided at an entire circumference, andthe cantilevers are placed in a state extending along the aforesaidouter edge of reflecting portion.

[0018] In the same diaphragm structure, an incline portion with a crosssectional shape rising diagonally is provided outward from the outercircumference edge of the aforesaid reflecting portion, a flat portionwith a cross-sectional shape extending in a horizontal direction furtherto an outside from an outer circumference of the aforesaid inclineportion is provided at the entire circumference, and the cantilevers areplaced at the aforesaid flat portion in a state extending alongfollowing the outer circumference edge of the aforesaid vibratingsection.

[0019] In the same diaphragm structure, a falling portion with a crosssectional shape at the right angle or an angle substantially the rightangle is provided at an entire circumference of the outer circumferenceedge of the aforesaid reflecting portion, a flat portion with a crosssectional shape extending in a horizontal direction further toward anoutside from an outer circumference portion of the aforesaid fallingportion is provided at the entire circumference, and the cantilevers areplaced at the aforesaid flat portion in a state extending along theouter circumference of the aforesaid vibrating section.

[0020] Further in the same diaphragm structure, a rising portion or afalling portion with a cross sectional shape rising or fallingvertically or diagonally, or made of an arc is provided at an outercircumference edge of the aforesaid reflecting portion, a flat portionwith a cross sectional shape extending,in the horizontal directionfurther to an outside from an outer circumference edge of the aforesaidrising portion or falling portion is provided along the entirecircumference, and the cantilevers are placed at the aforesaid flatportion in a state extending along the outer circumference shape of thevibrating section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a plane view showing a diaphragm of an optical-acoustictransducer being a first embodiment of this invention;

[0022]FIG. 2 is a cross sectional view showing the same diaphragm;

[0023]FIG. 3 is a sectional view showing an optical-acoustic transducerusing the same diaphragm;

[0024]FIG. 4 is a plane view showing a diaphragm of an optical-acoustictransducer being a second embodiment of this invention;

[0025]FIG. 5 is a cross sectional view showing the same diaphragm;

[0026]FIG. 6 is a cross sectional view showing an optical-acoustictransducer using the same diaphragm;

[0027]FIG. 7 is a plan view showing a diaphragm of an optical-acoustictransducer being a third embodiment of this invention;

[0028]FIG. 8 is a cross sectional view showing the same diaphragm;

[0029]FIG. 9 is a cross sectional view showing an optical-acoustictransducer using the same diaphragm;

[0030]FIG. 10 is a plane view showing a diaphragm of an optical-acoustictransducer being a fourth embodiment of this invention;

[0031]FIG. 11 is a cross sectional view showing the same diaphragm;

[0032]FIG. 12 is a cross sectional view showing an optical-acoustictransducer using the same diaphragm;

[0033]FIG. 13 is a cross sectional view showing an example of aconventional optical-acoustic transducer;

[0034]FIG. 14 is a cross sectional view showing another example of aconventional optical-acoustic transducer;

[0035]FIG. 15 is a cross sectional view showing still another example ofa conventional optical-acoustic transducer;

[0036]FIG. 16 is a plane view showing yet another example of aconventional optical-acoustic transducer; and

[0037]FIG. 17 is a cross sectional view showing part of the sameoptical-acoustic transducer.

EMBODIMENTS OF THE INVENTION

[0038] Embodiments of this invention will be explained based on thedrawings. A diaphragm in each embodiment is produced by cutting a resinfilm in a flat sheet form with thickness of about 9μ to about 25μ as itis, or it is produced by cutting after thermal pressure forming.

[0039]FIG. 1 is a plane view showing a diaphragm of an optical-acoustictransducer being a first embodiment of this invention, FIG. 2 is a crosssectional view showing the same diaphragm, and FIG. 3 is a crosssectional view showing an optical-acoustic transducer using the samediaphragm.

[0040] A diaphragm 1 shown in the drawings is a flat sheet withthickness of 15μ and a diameter of 6 mm, and the diaphragm 1 is producedby applying slit working and attaching a ring 3 to a supporting portion1 b of an outer circumference portion by bonding, whereby a desiredamplitude can be obtained.

[0041] Specifically, three arc-shaped inner slits 2 a, 2 a . . . andthree arc-shaped outer slits 2 b, 2 b . . . are equidistantly formedrespectively, and the inner slits 2 a and the outer slits 2 b areconnected with radial slits 2 c, whereby cantilevers 1 c, 1 c, . . .surrounded by the slits are obtained, and the cantilevers construct asuspension of a vibrating section 1 a surrounded by the inner slits 2 a,2 a, . . . The long dashed short dashed lines illustrated at the flatportion in the cross sectional view in FIG. 2 shows a position and widthof the slit.

[0042] Since the cantilevers extend along an outer circumference of thevibrating section, the vibrating section does not become so small evenif compliance is made larger by increasing the length of thecantilevers, and as a result, the highly sensitive and compact diaphragmof the optical-acoustic transducer can be obtained.

[0043] As shown in FIG. 3, the supporting portion 1 b of the diaphragm 1is fixed to the frame 4 via the ring 3, and the light emitter 5 and thelight receiver 6 are fixed to the frame 4, whereby the optical-acoustictransducer is completed. Metal vapor deposition is applied to a portionf or reflecting light from the light emitter 5 of the diaphragm 1.

[0044]FIG. 4 is a plan view showing a diaphragm of an optical-acoustictransducer being a second embodiment of this s invention, FIG. 5 is across sectional view showing the same diaphragm, and FIG. 6 is a crosssectional view showing an optical-acoustic transducer using the samediaphragm. In this example, a film of thickness of about 15μ is formedas shown in FIG. 5, and slit working is applied thereto as in the firstembodiment, whereby a diaphragm 7 with a desired amplitudecharacteristic is obtained.

[0045] Explaining the details hereinafter, a plane portion is providedat a center, and an incline portion 7 d with rising of about 0.6 mm froman outer circumference portion of this plane portion is provided, and aflat portion, which is flat outward from an upper end portion of theincline portion 7 d in the horizontal direction, is provided. In thecase of this embodiment, the flat portion provided at an outside fromthe outer circumference portion of the aforesaid incline portion 7 d iscut with a circle with a diameter of 6 mm.

[0046] The width of the flat portion is 1 mm, and slits, which aresimilar to those in the first embodiment, are provided at the flatportion. Specifically, three arc-shaped inner slits 2 a, 2 a . . . andthree arc-shaped outer slits 2 b, 2 b . . . are equidistantly formedrespectively, and the inner slits 2 a and the outer slits 2 b areconnected with radial slits 2 c, whereby cantilevers 7 c, 7 c, . . .with the width of about 0.2 mm, which are surrounded by the slits, areobtained, and the cantilevers construct a suspension of a vibratingsection 7 a surrounded by the inner slits 2 a, 2 a, . . . .

[0047] The long dashed short dashed lines illustrated at the flatportion in the cross sectional view of FIG. 5 shows a position and widthof the slit. More specifically, metal vapor deposition is applied to areflecting surface of the vibrating section after the diaphragm isformed, and thereafter, slit work is performed in this embodiment. Asshown in FIG. 6, the supporting portion 7 b of the diaphragm 1 is fixedto the frame 4, and the light emitter 5 and the light receiver 6 arefixed to the frame 4, whereby the optical-acoustic transducer iscompleted. Since the inclined surface is provided at the vibratingsection of the diaphragm in this example, the rigidity of the vibratingsection is enhanced, and the optical-acoustic transducing characteristicis further improved.

[0048]FIG. 7 is a plane view showing a diaphragm of an optical-acoustictransducer being a third embodiment of this invention, FIG. 8 is a crosssectional view showing the same diaphragm, and FIG. 9 is a crosssectional view showing the optical-acoustic transducer using the samediaphragm. In this example, a reflecting portion 8 a formed in a domeshape with the diameter of 1.3 mm and the radius of curvature of 1.5 mmis provided at a center of a diaphragm 8 as shown in the cross sectionalview in FIG. 8. At the outermost circumference portion of this dome, afalling portion 8 b of the length of 0.5 mm is provided downward in thedrawing on the entire outer circumference of the dome, a flat portionwith the width of about 1.5 mm with the cross sectional shape extendingin the horizontal direction to an outside from a lower end of thefalling portion 8 b is provided at the entire circumference, and thisflat portion is cut with a circle with the diameter of 3 mm.

[0049] Slit working is applied to the spots outside from the fallingportion 8 b provided at the outer circumferential portion of theaforementioned dome, at spaces of predetermined dimensions as shown inthe plane view of FIG. 7, in the state extending along the outercircumference of the falling portion 8 b. Explaining in detail, in thecase of this embodiment, three inner slits 2 a, 2 a, . . . with thewidth of 4082 to 50μ, which are the arcs of substantially three equalparts (radius of curvature of 1.225 mm), are provided at the spot of theradius of 0.775 mm shown in the plane view which is outside the outercircumference of the dome.

[0050] Slit working constituted of arcs (radius of curvature of 1.425mm) with the same width as described above (4082 to 50μ) which aresubstantially three equal parts, is applied to the spot of the radius of1.425 mm outside the aforementioned inner slits 2 a, 2 a, . . . , toprovide three arc-shaped outer slits 2 b, 2 b, . . . , and slit workingis further applied such that the outer slits 2 b and the inner slits 2 aare connected with the radial slits 2 c as shown in the drawings. Thelong dashed short dashed lines illustrated at the flat portion in thecross sectional view of FIG. 8 shows a position and width of the slit.

[0051] A cantilever 8 c is formed by being surrounded by theaforementioned slits: the inner slit 2 a, the outer slit 2 b and theradial slit 2 c, and the cantilever 8 c becomes a suspension forsupporting the reflecting portion 8 a at a supporting portion 8 d.

[0052] In the case of this embodiment, the suspension is constructed bythree cantilevers 8 c in the form along the outer circumference of thereflecting portion 8 a, and the supporting portion 8 d of the flatportion, which is provided outside the outer slits 2 b, 2 b, . . . hasthe function of a margin to overlap or the like for the purpose offixing the diaphragm 8 to the ring 3, which is in the state as shown inthe cross sectional view of the explanatory view to have the structureof supporting the reflecting portion 8 a at the cantilevers 8 c, 8 c, .. . with the width of about 0.2 mm.

[0053] As shown in FIG. 9, the supporting portion 8 d of the diaphragm 8is fixed to the frame 4 via the ring 3, and the light emitter 5 and thelight receiver 6 are fixed to the frame 4, whereby the optical-acoustictransducer is completed. Since the reflecting portion is in the domeshape in this embodiment, the optical-acoustic transducingcharacteristic is further improved.

[0054]FIG. 10 is a plane view showing a diaphragm of an optical-acoustictransducer as a fourth embodiment of this invention, FIG. 11 is a crosssectional view showing the same diaphragm, and FIG. 12 is a crosssectional view showing the optical-acoustic transducer using the samediaphragm. As shown in the drawings, a reflecting section 9 a formed ina dome shape with the diameter of 1.3 mm and the radius of curvature of1.5 mm is provided at a center of a diaphragm 9.

[0055] An incline portion 9 b rising diagonally at an inclination of 45degrees from an outer circumference portion of this dome, namely, thereflecting portion 9 a, is provided, and a top end portion of theincline portion 9 b is set to have the diameter of about 3.2 mm, across-sectional arc portion 9 c with the radius of 0.24 mm is providedwith this top end portion as a tangential line, and a flat portionextending in the direction of 90 degrees outside the cross sectional arcportion 9 c, namely, in the horizontal direction shown in the drawing.

[0056] The diameter of the outer circumferential portion of the crosssectional arc portion 9 c provided at the top end portion of theaforementioned incline portion 9 b is 4 mm. In the case of thisembodiment, the flat portion provided outside from the outercircumferential portion of the aforementioned cross sectional arcportion 9 c is cut with the circle with the diameter of 6 mm.Accordingly, the width of the flat portion is 1 mm, and slits areprovided at this flat portion as shown in FIG. 10.

[0057] Explaining in detail, three of the arc-shaped inner slits 2 a, 2a . . . with the width of 4082 to 50μ, which are substantially threeequal parts, are provided at the spots of the radius of 2.215 mm, threeof the arc-shaped outer slits 2 b, 2 b . . . with the width of 40μ to50μ, which are substantially three equal parts,. are formed at the spotsof the radius of 2.375 mm, and the inner slits 2 a and the outer slits 2b are connected with the radial slits 2 c, whereby the cantilevers 9 d,9 d . . . surrounded by the slit are obtained, and the cantileversconstruct a suspension of the vibrating section surrounded by the innerslits 2 a, 2 a . . .

[0058] The flat portion provided outside the outer slits 2 b, 2 b . . .becomes a support portion 9 e having the function of a margin to overlapor the like for the purpose of fixing the diaphragm 9 to the ring 3 orthe like. The cantilevers 9 d with the width of about 0.2 mm have thefunction of suspension and support the reflecting portion 9 a and theincline portion 9 b as shown in the cross sectional view in FIG. 11. Thelong dashed and short dashed lines illustrated at the flat portion inthe cross sectional view in FIG. 11 show the position and width of theslit.

[0059] Since the back sides of the diaphragms of the aforementionedthird and fourth embodiment, namely, the surfaces inside the domesbecome the reflecting surfaces for laser light, metal vapor depositionor the like of nickel, aluminum, or the like is applied to thisreflecting surface. It is possible to perform metal vapor depositiononly for the reflecting portions 8 a and 9 a by masking. In the case ofthese embodiments, slit working is performed by using excimer laser, yaglaser, carbon dioxide laser and the like, and it was possible to attainthe intended purpose in any laser.

[0060] The aforementioned third and the forth embodiment are diaphragmswith the vibrating section such as the reflecting portion being formedthree-dimensionally, but it turns out that the invention is applicableto plane diaphragms as in the first embodiment.

ADVANTAGES OF THE INVENTION

[0061] According to the diaphragm structure of the present invention,the cantilever-shaped suspension is naturally placed outside thediaphragm. It is obviously easier to secure the length of the cantileverin the outer circumferential part (outside) than in the innercircumferential part (inside). Namely, it is possible to set thecompliance of the suspension in the cantilever form at a higher level,which results in the advantages of having the basic structure capable ofsecuring large amplitude and the area of the vibrating section of thediaphragm does not have to be reduced significantly due to thecantilevers.

[0062] It is obvious that if the area of the diaphragm is reduced to theminimum limit as in the third embodiment, it becomes advantageous thatthe dome portion of the reflecting portion 8 a also serves as thevibrating section. In this situation, it is not necessary to place thesuspension by applying slit working to the reflecting portion, namely,the vibrating section as in the prior art, and the suspension is placedat the outer circumference portion of the vibrating section, whereby theadvantage of capable of reducing the diaphragm to the limit is provided.Further, by providing the incline portion 9 b outside the reflectingportion 9 a as in the fourth embodiment, strength of the diaphragm isincreased and the surface area of the vibrating section is increased asa matter of course.

[0063] Namely, the pressure receiving area for sound pressure increaseswith high strength, and the cross-sectional arc portion 9 c, or therising portion, or the falling portion or the like is provided at theouter circumference portion of the incline portion 9 b, thereby makingit possible to increase strength of the outer circumference portion ofthe diaphragm is increased and increase the surface area of thediaphragm at the same time. Accordingly, it becomes possible to obtainthe diaphragm with high sensitivity, high sound quality and thestructure facilitating amplitude, and thus the effect of obtaining thediaphragm with higher performance.

[0064] The above-described Japanese Patent Application No. 2001-184530already discloses that the deformation of the reflecting portion can beeffectively prevented by giving the rib structure to the outermostcircumference portion of the reflecting portion, and it is naturallypreferable to enhance rigidity of the rib structure by providing thestructure of the rising portion or the falling portion at the crosssection of the dome outer circumference portion.

[0065] However, if the reflecting portion 9 a is reduced to the minimum,namely, if the diaphragm is reduced to the minimum, it is obvious thatproviding the rising portion in the diagonal direction increases thesize of the diaphragm, which provides the structure contradictingminimization.

[0066] Accordingly, increase in size can be avoided by providing therising portion in the vertical form at the outer circumference portionof the dome of the reflecting portion. It is possible to provide therising portion in the opposite direction to the dome shape, namely,substantially vertical in the upward direction shown in the drawings,but it becomes clear that in this direction, a film is easily broken inthe film forming, and it also becomes possible that even if it can beformed, the film at the rising portion tends to be thin in thisdirection and the rib effect reduces by half.

[0067] For this disadvantage, it becomes clear that by providing thefalling portion 8b at the outer circumference portion of the dome of thereflecting portion 8 a as in the third embodiment, the film breakage iseliminated, satisfactory film thickness can be obtained, the rib effectcan be sufficiently exhibited, and the effect is exhibited inenhancement of the performance of the diaphragm.

[0068] When there is a room in dimension, it is natural that the risingportion in the diagonal direction is naturally effective. Accordingly,the mode of the diaphragm shown in the fourth embodiment results inreinforcement of the reflecting portion as well as increase in thestrength of the diaphragm, and therefore it has the advantage ofimproving the film forming performance and further increasing thestrength of the diaphragm.

[0069] According to the structure as that of the present invention, inproduction of the film forming die used in forming the diaphragm, it ispossible to produce it only by lathe-working, and its shape is simple.Accordingly, the advantage of sharply reducing the working cost isprovided, the cost of the die is reduced more sharply than in the priorart, the fact that the slit working portion is the flat portioncontributes to improvement in working precision of the slit width, andthus improvement in quality and performance as well as cost reductioncan be achieved.

1. An optical-acoustic transducer comprising a diaphragm with a supportportion of a vibrating section being connected to the vibrating sectionvibrated with sound, with the suitable number of cantilevers, and alight emitter and a light receiver placed to oppose to a lightreflecting portion formed at the vibrating section of the diaphragm, anddetecting a change in a position of the vibrating section following thevibration of said vibrating section by receiving light, irradiated fromsaid light emitter and reflected at the light reflecting portion of saidvibrating section, at said light receiving element, characterized inthat said cantilevers are formed by performing slit working for saiddiaphragm, and a portion between an outer circumference edge of saidvibrating section and inner circumference edges of said cantilevers anda portion between an inner circumference edge of said support portionand outer circumference edges of said cantilevers are partitioned bysaid slit working, and said cantilevers extend along a portion betweenan outer circumference of said vibrating section and an innercircumference of said support portion.
 2. The optical-acoustictransducer according to claim 1, characterized in that a slitpartitioning the portion between the outer circumference edge of saidvibrating section and the inner circumference edges of said cantileversand the portion between the inner circumference edge of said supportingportion and the outer circumference edges of said cantilevers eachcomprises: at least three arc-shaped inner slits formed at the outercircumference of the vibrating section; at least three arc-shaped outerslits existing outside the inner slits and formed at the innercircumference of said supporting portion; and radial slits each couplingone end of each inner slit and one end of the outer slit formed outsidethe other inner slit adjacent to the one end of the inner slit.
 3. Theoptical-acoustic transducer according to claim 2, characterized in thatone end of said cantilever is connected to said vibrating section by aportion between the one end of each of the inner slits at a side towhich the radial slit is coupled and the one end of the other inner slitadjacent to said inner slit at the side to which the radial slit is notcoupled, and the other end of the cantilever is connected to saidsupporting portion by a portion between the one end of each of the outerslits at a side to which the radial slit is coupled and the one end ofthe other outer slit adjacent to said outer slit at the side to whichthe radial slit is not coupled.
 4. The optical-acoustic transduceraccording to claim 1, characterized in that a flat portion extendinghorizontally to an outside from an outer circumference edge of the lightreflecting portion forming said vibrating section is provided at anentire circumference of the outer circumference edge of the lightreflecting portion forming said vibrating section, and the cantileversextending along the outer circumference of said vibrating section areformed at the flat portion.
 5. The optical-acoustic transducer accordingto claim 1, characterized in that an incline portion rising in adiagonal direction from an outer circumference edge of the lightreflecting portion forming said vibrating section is provided at anentire circumference of the outer circumference edge of the lightreflecting portion forming said vibrating section, a flat portionextending horizontally to an outside from an upper end circumferenceedge of said incline portion is further provided at the entirecircumference, and the cantilevers extending along the outercircumference of said vibrating section are formed at the flat portion.6. The optical-acoustic transducer according to claim 1, characterizedin that a falling portion falling downward at the right angle or anangle near the right angle from an outer circumference edge of the lightreflecting portion forming said vibrating section is provided at anentire circumference of the outer circumference edge of the lightreflecting portion forming said vibrating section, a flat portionextending horizontally toward an outside from a lower end circumferenceedge of said falling portion is provided at the entire circumference,and the cantilevers extending along the outer circumference of saidvibrating section are formed at the flat portion.
 7. Theoptical-acoustic transducer according to claim 1, characterized in thata rising portion rising vertically or diagonally upward from an outercircumference edge of the light reflecting portion forming saidvibrating section is provided along an entire circumference, a fallingportion falling downward in an arc form from an upper end circumferenceedge of said rising portion is provided along an entire circumference, aflat portion extending horizontally to an outside from an lower endcircumference edge of said falling portion is provided at an entirecircumference, and the cantilevers extending along the outercircumference of said vibrating section are formed at the flat portion.